Light emitting devices, such as light emitting diodes (LEDs) and laser diodes, which use a Group III-V or Group II-VI compound semiconductor material, may render various colors such as red, green, blue, and ultraviolet by virtue of development of thin film growth technologies and device materials. It may also be possible to produce white light at high efficiency using fluorescent materials or through color mixing. Further, the light emitting devices have advantages, such as low power consumption, semi-permanent lifespan, fast response time, safety, and environmental friendliness as compared to conventional light sources, such as fluorescent lamps and incandescent lamps.
Therefore, these light emitting devices are increasingly applied to transmission modules of optical communication units, light emitting diode backlights as a replacement for cold cathode fluorescent lamps (CCFLs) constituting backlights of liquid crystal display (LCD) devices, and lighting apparatuses using white light emitting diodes as a replacement for fluorescent lamps or incandescent lamps, headlights for vehicles and traffic lights.
FIG. 1 is a cross-sectional view of a conventional light emitting device. FIG. 2 is a top image view illustrating current spreading of the light emitting device in FIG. 1. FIG. 1 illustrates a cross-sectional view taken along line A-A of FIG. 2.
Referring to FIG. 1, the conventional light emitting device, which is designated by reference numeral “1”, includes a substrate 10, and a light emitting structure 20 disposed on the substrate 10. The light emitting structure 20 includes a first conductivity type semiconductor layer 22, an active layer 24, and a second conductivity type semiconductor layer 26. The light emitting structure 20 has a mesa etching region M where portions of the second conductivity type semiconductor layer 26, active layer 24, and first conductivity type semiconductor layer 22 are removed through etching.
A first electrode 30 is disposed on a portion of the first conductivity type semiconductor layer 22 exposed through the etching region M. A second electrode 40 is disposed on an unetched portion of the second conductivity type semiconductor layer 26. A transparent electrode layer 50 is disposed between the second conductivity type semiconductor layer 26 and the second electrode 40.
However, the conventional light emitting device 1 may have a following problem.
Referring to FIG. 2, current from the second conductivity type semiconductor layer 26 flows while bypassing the mesa etching region M because the transparent electrode layer 50 is not present in the mesa etching region M. As a result, current spreading is ineffective and, as such, there may be a phenomenon in which current is concentrated around the second electrode 40.